> So my understanding based on what I have read and what you say here...
>=20
> PAGESEL is needed to set PCLATH before each GOTO/CALL unless the target
> is in the same CODE block. The call into interrupt does NOT change PCLATH=
,
> so there is a need to do it _within_ the handler.

There is a standard handler which you will see in a lot of PIC16 code which=
 saves the PCLATH, W and STATUS register, and restores them all at the end =
of the interrupt.

Just because the CALL or GOTO is in a CODE block does not mean you will not=
 need to use PAGESEL within the CODE block. The defining reason for using P=
AGESEL is if the CALL or GOTO is sending the program outside the current pa=
ge of Flash ROM, and the size of this page various by chip. YOU need to loo=
k at the datasheet for the chip you are using and make sure that YOU deal w=
ith this in your code.

On the other hand, you could download the development environment developed=
 by a past member of this group. Using macros he developed you ALWAYS put h=
is equivalent of PAGESEL before EVERY CALL or GOTO, and the macro knows whe=
re it is in the code, and ONLY IF NECESSARY generates the appropriate instr=
uctions that emulate the PAGESEL macro.

See http://www.embedinc.com/pic/ for more information.

>=20
> RETURN/RETFIE don't use PCLATH, the entire address comes from the stack.

Correct.

>=20
> The only way to avoid these issues is to use absolute code (or to write c=
ode
> in a way that removes all of the relocatable code benefits)

WRONG - you will still have the same issue with CALL, GOTO and interrupts w=
hen using absolute mode. Absolute Mode and Relocatable Mode are purely asse=
mbler and linker modes, the processor doesn't have different modes in its s=
ilicon instruction set.

>=20
> A remaining question... does RETURN/RETFIE reset PCLATH? In the case of
> RETURN, it can be reset (as you know when the CALL happened) but in the
> case of RETFIE, I guess that you store the PCLATH register just like W, F=
SR
> and STATUS?

No. The only way to set PCLATH to anything is to deliberately load it yours=
elf. RETURN/RETFIE only reload the program counter with the address that wa=
s pushed onto the stack. In the case of RETFIE see my comments above.




--=20
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